The present applicant previously proposed various ideas for guiding the solar rays or artificial light focused by a lense or the like into an optical conductor and thereby transmitting it onto an optional, desired place through the optical conductor for the purpose of illumination or for other uses. Such a process would make it possible to by-pass and take out the light-energy transmitted through the optical conductor at the half-way point of transmission. Thereby the effect of the light-energy's use would be increased. Such a device would broaden the use of light energy.